Cloning and characterization of the erg1 gene of Trichoderma harzianum: effect of the erg1 silencing on ergosterol biosynthesis and resistance to terbinafine

Trichoderma species are commonly used as biocontrol agents of different plant-pathogenic fungi. Terpene compounds are involved in the biocontrol process due to their antifungal properties (e.g., ergokonins and viridins) but additionally their structural function in the cell membranes (ergosterol) is essential. We report here the characterization of the T. harzianum erg1 gene, encoding a squalene epoxidase, a key enzyme in the biosynthesis of triterpene derivatives such as ergosterol. In T. harzianum the partial silencing of the erg1 gene gave rise to transformants with a higher level of sensitivity to terbinafine, an antifungal compound that acts specifically over the squalene epoxidase activity. In addition, these silenced transformants produced lower levels of ergosterol than the wild type strain. Finally, the silencing of the erg1 gene resulted in an increase in the expression level of the erg7 gene that encodes the oxidosqualene lanosterol-cyclase, another enzyme of the terpene biosynthesis pathway.

Cloning and characterization of the erg1 gene of Trichoderma harzianum: Effect of the erg1 silencing on ergosterol biosynthesis and resistance to terbinafine

Trichoderma species are commonly used as biocontrol agents of different plant-pathogenic fungi. Terpene compounds are involved in the biocontrol process due to their antifungal properties (e.g., ergokonins and viridins) but additionally their structural function in the cell membranes (ergosterol) is essential. We report here the characterization of the T. harzianum erg1 gene, encoding a squalene epoxidase, a key enzyme in the biosynthesis of triterpene derivatives such as ergosterol. In T. harzianum the partial silencing of the erg1 gene gave rise to transformants with a higher level of sensitivity to terbinafine, an antifungal compound that acts specifically over the squalene epoxidase activity. In addition, these silenced transformants produced lower levels of ergosterol than the wild type strain. Finally, the silencing of the erg1 gene resulted in an increase in the expression level of the erg7 gene that encodes the oxidosqualene lanosterol-cyclase, another enzyme of the terpene biosynthesis pathway.

ThPTR2, a di/tri-peptide transporter gene from Trichoderma harzianum

The generation of a wide ESTs library and database from Trichoderma harzianum CECT 2413 was the base for identifying the gene ThPTR2, coding for a PTR family di/tri-peptide transporter. The deduced protein sequence of the ThPTR2 gene showed the conserved motifs and also the 12 transmembrane domains typical of the PTR transporters. The highest level of ThPTR2 expression was found when the fungus was grown in chitin as sole carbon source. We also found that ThPTR2 expression was increased when Trichoderma interacted directly in solid medium with the plant-pathogenic fungus Botrytis cinerea, showing that ThPTR2 is involved in the mycoparasitic process. Additionally, its expression was triggered by nitrogen starvation and a higher level of expression was also found when Trichoderma was grown in secondary nitrogen sources like allantoin, yeast extract, and urea. However, no difference was found when Trichoderma was grown in presence or absence of glucose as carbon source. Strain T34-15, a transformant that overexpressed the ThPTR2 gene, showed about a 2-fold increase in the uptake of the dipeptide Leu-Leu. Additionally, two transformants from the strain Trichoderma longibrachiatum T52 that overexpressed ThPTR2 were also studied, confirming the role of this gene in peptide transport. Other homologous genes to ThPTR2 were identified in other Trichoderma strains. ThPTR2 is the first experimentally confirmed PTR family transporter gene from filamentous fungi.

Detection of putative peptide synthetase genes inTrichodermaspecies: Application of this method to the cloning of a gene fromT. harzianumCECT 2413

Some of the secondary metabolites produced by Trichoderma, such as the peptaibols and other antibiotics, have a peptide structure and in their biosynthesis are involved proteins belonging to the Non-Ribosomal Peptide Synthetase family. In the present work, a PCR-mediated strategy was used to clone a region corresponding to an adenylation domain of a peptide synthetase (PS) gene from 10 different strains of Trichoderma. In addition, and using the fragment isolated by PCR from T. harzianum CECT 2413 as a probe, a fragment of 19.0 kb corresponding to a PS-encoding gene named salps1, including a 1.5 kb fragment of the promoter, was cloned and sequenced. The cloned region of salps1 contains four complete, and a fifth incomplete, modules, in which are found the adenylation, thiolation and condensation domains, but also an additional epimerization domain at the C-terminal end of the first module. The analysis of the Salps1 protein sequence, taking into consideration published data, suggests that it is neither a peptaibol synthetase nor a protein involved in siderophore biosynthesis. The presence of two breaks in the open reading frame and the expression of this gene under nitrogen starvation conditions suggest that salps1 could be a pseudogene.

Mg,Al layered double hydroxides with intercalated indomethacin: Synthesis, characterization, and pharmacological study

Magnesium aluminium layered double hydroxides (LDH) with a molar Mg/Al ratio of 2.0 have been prepared with intercalated indomethacin following two routes: reconstruction from a previously calcined Mg(2)Al-CO(3) LDH, and coprecipitation from the corresponding chlorides. The solids have been characterized by powder X-ray diffraction, FTIR, and (13)C CP/MAS NMR spectroscopies and thermal stability (differential thermal analysis and thermogravimetric analysis). Intercalation of the drug is attained by both routes; however, while coprecipitation leads to a single layered structure, contamination with another layered MgAl-CO(3) phase occurs by the reconstruction method. The amount of drug intercalated, as well as the height of the gallery, are larger by the coprecipitation than by the reconstruction one. The data obtained support a somewhat tilted, upwards orientation of the drug molecules forming an interdigited bilayer, in the case of the sample prepared by coprecipitation, with the carboxylate groups pointing towards the hydroxyl layers. However, in the case of the sample prepared by reconstruction, the molecules are forming a tilted, upwards monolayer. The solids prepared are stable up to 250 degrees C. Pharmacological studies in vivo show that intercalation of the drug in the LDH reduces the ulcerating damage of the drug.

Synthesis and Characterization of New Mg2Al-Paratungstate Layered Double Hydroxides

Layered double hydroxides (LDHs, or hydrotalcites) with Mg(2+) and Al(3+) cations in the mixed metal hydroxide layer and paratungstate anions in the interlayer have been prepared. Different methods have been followed: anion exchange with Mg,Al LDHs originally containing nitrate or adipate, reconstruction of the LDH structure from a mildly calcined Mg(2)Al-CO(3) LDH, and coprecipitation. In all cases, the tungsten precursor salt was (NH(4))(10)H(2)W(12)O(42). The prepared solids have been characterized by elemental chemical analysis, powder X-ray diffraction (PXRD), FT-IR spectroscopy, thermogravimetric (TG) and differential thermal (DTA) analyses, scanning electron microscopy (SEM) with EDX (energy-dispersive X-ray analysis), and nitrogen adsorption at -196 degrees C for surface area and surface texture. Most of the synthesis methods used, especially anion exchange starting from a Mg(2)Al-NO(3) precursor at low temperature and short reaction times, lead to formation of a hydrotalcite with a gallery height of 9.8 A; increasing the reaction temperature to 70-100 degrees C and maintaining short contact times leads to a solid with a gallery height of 7.8 A. Both phases have been identified as a result of the intercalation of W(7)O(24)(6)(-) species in different orientations in the interlayer space. If the time of synthesis or the temperature is increased, a more stable phase, with a gallery height of 5.2 A corresponding to a solid with intercalated W(7)O(24)(6)(-), is formed, probably with grafting of the interlayer anion on the brucite-like layers. All systems are microporous. Calcination at 300 degrees C leads to amorphous species, and crystallized MgWO(4) is observed at 700 degrees C.

Expression of a synthetic copy of the bovine chymosin gene in Aspergillus awamori from constitutive and pH-regulated promoters and secretion using two different pre-pro sequences

A copy of the bovine chymosin gene (chy) with a codon usage optimized for its expression in Aspergillus awamori was constructed starting from synthetic oligonucleotides. To study the ability of this filamentous fungus to secrete bovine prochymosin, two plasmids were constructed in which the transcriptional, translational, and secretory control regions of the A. nidulans gpdA gene and pepB genes were coupled to either preprochymosin or prochymosin genes. Secretion of a protein enzymatically and immunologically indistinguishable from bovine chymosin was achieved in A. awamori transformants with each of these constructions. In all cases, the primary translation product (40.5 kDa) was self-processed to a mature chymosin polypeptide having a molecular weight of 35.6 kDa. Immunological assays indicated that most of the chymosin was secreted to the extracellular medium. Hybridization analysis of genomic DNA from chymosin transformants showed chromosomal integration of prochymosin sequences and, in some transformants, multiple copies of the expression cassettes were observed. Expression from the gpdA promoter was constitutive, whereas expression from the pepB promoter was strongly influenced by pH. A very high expression from the pepB promoter was observed during the growth phase. The A. awamori pepB gene terminator was more favorable for chymosin production than the S. cerevisiae CYC1 terminator.

Intercalation of [Cr(C2O4)3]3 - complex in mg,al layered double hydroxides

A Mg,Al layered double hydroxide (LDH) with [Cr(C(2)O(4))(3)](3)(-) anions in the interlayer has been synthesized following two different routes: reconstruction from a mildly calcined Mg,Al-carbonate LDH, and anion exchange from a Mg,Al-nitrate LDH. The solids prepared have been characterized by elemental chemical analysis, powder X-ray diffraction, FT-IR and UV-vis/DR (diffuse reflectance) spectroscopies, thermal methods, nitrogen adsorption at -196 degrees C, and FT-IR monitoring of pyridine adsorption. The results obtained indicate that the most appropriate method is anion exchange, leading to a well crystallized LDH with an interlayer spacing of 10 A. Due to the high pH value (>8) of the solution in the reconstruction method, however, a polyphasic system is obtained, where, in addition to a phase with the LDH structure, amorphous magnesium oxalate and chromium oxohydroxides are also formed due to hydrolysis of the complex. The interlayer complex is stable up to 200 degrees C, but the layered structure is stable up to 330 degrees C, probably because of the presence of interlayer oxalate anions formed during decomposition of the complex. Calcination leads to oxidation of Cr(3+) ions to the six-valent state, which reverts to Cr(3+) when the calcination temperature is further increased.

[Laparoscopic resection of hepatic hydatid cyst under general anesthesia with remifentanil infusion]

We report the case of a 52-year-old woman who underwent scheduled laparoscopic resection of a hydatid liver cyst under general anesthesia by infusion of remifentanil and sevoflurane. Surgery was uneventful, although invasive monitoring was required, just as it would have been in major open abdominal surgery, given the risk of bleeding secondary to organ manipulation, the risk of anaphylactic shock related to the etiology of the cyst and the possibility of gas embolism related to laparoscopy. The concept of "minimally invasive" surgery has developed thanks to continued progress in laparoscopy. The considerable advantages of such procedures in comparison with "open" or "conventional" surgery has led to their use with organs such as the liver, which in principle require caution. In such cases, the anesthesiologist must take an approach that is not as simple or minimalist as the term "minimally invasive" might lead us to expect.

Anaerobic degradation kinetics of a cholesteryl ester

The most important components of wool scouring effluent grease are esters of sterols. Cholesteryl palmitate (CP) is the main ester in this grease. In this paper, the influence of the ester concentration in the anaerobic digestion and the relative rate of the different degradation steps, are studied. The experiment was carried out to measure methane production in the anaerobic degradation of acetate, palmitic acid (PA) and CP. A first-order kinetic model was assumed for hydrolysis and Monod models were assumed for both the methanogenic and acetogenic steps. Maximum hydrolysis rate was found to be around 20 times faster than the maximum methanogenic reaction rate during the experience. The lanolin emulsion drop size effect was also evaluated employing fine and coarse stock lanolin emulsions and no adapted sludge. Concentrations of 13.7 to 4.6 gCOD x l(-1) were employed. In a previous study, the effect of palmitic acid emulsion size was found important when similar sludge was tested. When esters are degraded, a significant effect of drop size on the degradation rate was not found. The difference between CP and PA emulsions behavior could be due to the fact that cholesterol produced during the ester degradation has a protective effect on the sludge.

The cefT gene of Acremonium chrysogenum C10 encodes a putative multidrug efflux pump protein that significantly increases cephalosporin C production

Transcriptional analysis of the region downstream of the pcbAB gene (which encodes the alpha-aminoadipyl-cysteinyl-valine synthetase involved in cephalosporin synthesis) of Acremonium chrysogenum revealed the presence of two different transcripts corresponding to two new ORFs. ORF3 encodes a putative D-hydroxyacid dehydrogenase and cefT (for transmembrane protein) encodes a multidrug efflux pump belonging to the Major Facilitator Superfamily (MFS) of membrane proteins. The CefT protein has 12 transmembrane segments (TMS) and contains motifs A, B, C, D2 and G characteristic of the Drug:H(+) antiporter 12-TMS group of the major facilitator superfamily. The CefT protein confers resistance to some toxic organic acids, including isovaleric acid and phenylacetic acid. Targeted inactivation of ORF3 and cefT by gene replacement showed that they are not essential for cephalosporin biosynthesis. However, amplification of the cefT gene results in increments of up to 100% in cephalosporin production in the A. chrysogenum C10 strain. Amplification of a truncated form of the cefT insert did not lead to cephalosporin overproduction. It seems that the CefT protein is involved in cephalosporin export from A. chrysogenum or in transmembrane signal transduction, and that there are redundant systems involved in cephalosporin export.

A procedure for the standardization of gamma reference sources for quality assurance in activity measurements of radiopharmaceuticals

A simplified procedure for the standardization of gamma reference sources, for use in quality assurance of activity measurements during production and application of radiopharmaceuticals in Cuban nuclear medicine laboratories, is described. The method is based on the reliable achievement of consistent measurements by both gamma-spectrometry and ionization chamber techniques, and allows to obtain reference sources with uncertainties lower than 2%. Experimental setup, validation procedure and typical results obtained for 99mTc, 131I, 201Tl and 153Sm are described and discussed. The method will serve also as a secondary reference system for radioactivity measurements in the country.

A follow-up study on micronucleus frequency in Spanish agricultural workers exposed to pesticides

To determine whether occupational exposure to a complex mixture of pesticides results in a significant increase in the level of cytogenetic damage, a follow-up study was planned on 39 greenhouse workers from Almería (southeastern Spain). Taking into account that pesticide exposure can be season-related, two blood samples were taken from each individual at different times: one in a period of high exposure (sample A, spring-summer) and the other in a period of lower exposure (sample B, autumn-winter). Using the cytokinesis block micronucleus technique the frequency of binucleated cells with micronuclei (BNMN) and the cytokinesis blocked proliferation index (CBPI) were determined in peripheral blood lymphocytes. The results obtained indicate that there were no statistically significant differences in BNMN frequencies between the two sampling periods nor between exposed and controls. ANCOVA analysis of repeated measures revealed that the age of the individuals showed a direct relation with BNMN in the first study period. With regard to CBPI, a significant and season-related effect was found.

Subcellular localization of the homocitrate synthase in Penicillium chrysogenum

There are conflicting reports regarding the cellular localization in Saccharomyces cerevisiae and filamentous fungi of homocitrate synthase, the first enzyme in the lysine biosynthetic pathway. The homocitrate synthase (HS) gene (lys1) of Penicillium chrysogenum was disrupted in three transformants (HS(-)) of the Wis 54-1255 pyrG strain. The three mutants named HS1(-), HS2(-) and HS3(-) all lacked homocitrate synthase activity and showed lysine auxotrophy, indicating that there is a single gene for homocitrate synthase in P. chrysogenum. The lys1 ORF was fused in frame to the gene for the green fluorescent protein (GFP) gene of the jellyfish Aequorea victoria. Homocitrate synthase-deficient mutants transformed with a plasmid containing the lys1-GFP fusion recovered prototrophy and showed similar levels of homocitrate synthase activity to the parental strain Wis 54-1255, indicating that the hybrid protein retains the biological function of wild-type homocitrate synthase. Immunoblotting analysis revealed that the HS-GFP fusion protein is maintained intact and does not release the GFP moiety. Fluorescence microscopy analysis of the transformants showed that homocitrate synthase was mainly located in the cytoplasm in P. chrysogenum; in S. cerevisiae the enzyme is targeted to the nucleus. The control nuclear protein StuA was properly targeted to the nucleus when the StuA (targeting domain)-GFP hybrid protein was expressed in P. chrysogenum. The difference in localization of homocitrate synthase between P. chrysogenum and S. cerevisiae suggests that this protein may play a regulatory function, in addition to its catalytic function, in S. cerevisiae but not in P. chrysogenum.

Characterization of the gdhA gene from the phytopathogen Botrytis cinerea

A 3.48-kb DNA region containing the gdhA gene, which codifies the NADP-dependent glutamate dehydrogenase enzyme from Botrytis cinerea, has been cloned and characterized. A fragment of 2351 nucleotides was sequenced and found to contain an ORF of 1350 bp that encodes a protein of 450 amino acids. The gene, containing two introns that showed polymorphic size between them, was located by pulsed-field gel electrophoresis in chromosome X in seven strains, which were isolated from several hosts and had different levels of pathogenesis. The protein was similar to the gdhA of various other organisms, with nine highly conserved motifs that included the known active site sequence. The cloned gene was proven to be functional since it complemented two different Aspergillus nidulans gdhA mutants, restoring high levels of NADP-dependent glutamate dehydrogenase activity to the transformants. gdhA was transcribed as a monocistronic transcript of 1.7 kb starting at an A or a T, located 40 or 47 bp, respectively, upstream from the initial ATG codon of the ORF. Transcription levels of the gdhA gene were high during the rapid growth phase. Very high expression levels of the gdhA gene were observed in media with asparagine as the nitrogen source, whereas glutamic acid repressed transcription of the gdhA gene. Similarly high levels of gdhA gene transcription were observed in media with acetate as the carbon source, while glycerol strongly repressed gdhA gene transcription. These results indicate that expression of the gdhA gene is subject to strong nitrogen and carbon regulation at the transcriptional level.

Cytogenetic analysis of Greek farmers using the micronucleus assay in peripheral lymphocytes and buccal cells

The potential cytogenetic damage associated with pesticide use in Greek agricultural workers was evaluated using micronuclei (MN) as biomarkers in lymphocytes of peripheral blood and exfoliated cells of the buccal mucosa. In addition, the effects of pesticide exposure and other variables on the cytokinesis block proliferation index (CBPI) in lymphocytes were also evaluated. Both the exposed and control individuals were selected from Nea Makri, a village near Athens (Greece). This location was selected for its high greenhouse density. Micronuclei were analysed in 50 agricultural workers exposed to pesticides (30 men and 20 women) and in 66 non-exposed individuals that constituted the control group (41 men and 25 women). The comparison between workers and controls did not reveal any statistical significant difference in the MN frequency for either lymphocytes or buccal cells. Nevertheless, the multiple regression analysis revealed that the age and the interaction between gender and the number of X-ray examinations during the last 3 years preceding the sampling increased the number of MN in lymphocytes. Moreover, the results of the negative binomial regression analysis suggested that the level of MN in buccal cells could be reduced by the intake of fish, whilst being increased by olive oil consumption. Regarding CBPI, the value found in the exposed group was lower than in controls, the difference being statistically significant. On the other hand, CBPI was inversely associated with both age and X-ray exposure.

[Criteria for the diagnosis and treatment of chronic rhino-sinusitis in family medicine, otorhinolaryngology, and allergy services]

BACKGROUND

Rhinosinusitis is an inflammatory response affecting mucosa membrane of nasal cavity of one or more paranasal sinus. Its prevalence is of 14 and 5-13% in adults and children, respectively. Rhinosinusitis causes high rate of scholar and labor absenteeism.

OBJECTIVE

To know diagnostic and treatment criteria of rhinosinusitis in units of familial medicine, otolaryngology and allergy.

MATERIAL AND METHODS

A series of 25 patients randomly obtained from familial medicine units 21 and 28 of the IMSS, was studied. Diagnosis was assessed according to 1998 Consensus and computed tomography was considered the gold standard. It was performed to all patients and evaluated by a study-blind radiologist.

RESULTS

Diagnosis of rhinosinusitis was done by familial medicine unit in 68%, otolaryngology service in 40% and allergy service in 64%. Clinical criteria most used were nasal congestion and anterior and posterior nasal discharge. The more requested examination was computed tomography (38.7%) and in 30% of cases, medical treatment was not prescribed.

CONCLUSIONS

Familial physicians, otolaryngologists and allergists use, with low frequency, international criteria for diagnosis and treatment of chronic rhinosinusitis. Otolaryngologists perform other differential diagnosis.

Cloning and characterization of the gene cahB encoding a cephalosporin C acetylhydrolase from Acremonium chrysogenum

An important problem during the production of cephalosporin C by Acremonium chrysogenum is the hydrolysis of cephalosporin C to deacetylcephalosporin C, since the latter compound has no commercial value and represents an unwanted side-product. Characterization of the enzymatic process that gives rise to deacetylcephalosporin C will help to avoid the accumulation of this side-product. An extracellular cephalosporin C acetylhydrolase (CPC-AH) from Acremonium chrysogenum C10 was purified to near homogeneity. This enzyme had a molecular mass of 31 kDa, a pl of 4.0, and showed relatively little affinity for cephalosporin C (Km 33.7 mM). We sequenced twenty amino acids at the amino-terminal end; a probe based on this sequence was then used to clone the cephalosporin acetylhydrolase (cahB) gene. cahB encodes a pre-protein of 383 amino acids with a deduced molecular mass of 38,228 Da. The sequenced 20 amino acids of the purified protein corresponded to amino acids 107-127 deduced from the cahB gene, suggesting that mature CPC-AH results from processing of the pre-protein after Gln-106. cahB is located on chromosome VIII of A. chrysogenum C10 and is not linked to the cephalosporin early or late gene clusters. It is expressed as a single 1.4-kb transcript after 72 h of cultivation. Expression declined in batch cultures after 120 h even though CPC-AH activity was observed until 144 h. The CPC-AH protein resembles other wide-spectrum substrate fungal esterases that are functionally related to serine proteases. The cahB gene does not seem to be related to the cephalosporin biosynthesis genes and encodes an esterase active on several substrates in addition to cephalosporin C.

Micronuclei in peripheral blood lymphocytes and buccal epithelial cells of Polish farmers exposed to pesticides

In this biomonitoring study, we investigated whether an occupational exposure to a complex mixture of chemical pesticides produced a significant increase of micronuclei (MN) in both peripheral blood lymphocytes and buccal cells. Forty-nine male workers exposed to pesticides, from an agricultural area of Malopolska Region in Southern Poland, together with 50 men from the same area without indication of exposure to pesticides that served as controls, were used in this investigation. No statistically significant differences in the frequencies of cytogenetic damage were detected between exposed and control individuals, for either type of cells. The multiple linear regression analysis in the case of lymphocytes indicated that the studied cytogenetic endpoints were inversely influenced by alcohol; whilst a negative binomial regression, in the case of buccal cells, indicated that the MN values were directly influenced by the ingestion of red meat. An inverse negative relationship between the cytokinesis-block proliferation index and age, and a significant increase of miscarriages due to the exposure to pesticides were also observed.

Intrachromosomal recombination after targeted monocopy integration in Penicillium chrysogenum: stabilization of the direct repeats to prevent loss of the inserted gene

Monocopy systems obtained by targeted integration at the pyrG locus of P. chrysogenum led to the formation of unstable direct repeats in the genome. A previously isolated pyrG mutant was sequenced and the mutation was found to be located at nucleotide position 665 of the pyrG gene. A different pyrG mutation was introduced in vitro at the BamHI site of this gene. Recombination products arising from monocopy systems using the bleomycin/phleomycin resistance gene (ble) as a model were studied to elucidate the intrachromosomal recombination mechanisms. Experimental results showed that both gene conversion and deletion events occurred spontaneously at the integration site. Gene conversion products were obtained at a frequency of one in 3.4x10(4) viable transformant spores. When gene conversion occurred, the inserted exogenous gene was retained and was flanked by rearranged direct repeats of the pyrG gene, each containing at least one pyrG mutation. Deletion events resulted in the loss at high frequency of the inserted exogenous gene. Genetic stabilization of a monocopy system was obtained when both pyrG repeats (formed at the targeted integration site) contained at least one identical mutation, since in this case further recombinations can be easily counter-selected.

Targeted inactivation of the mecB gene, encoding cystathionine-gamma-lyase, shows that the reverse transsulfuration pathway is required for high-level cephalosporin biosynthesis in Acremonium chrysogenum C10 but not for methionine induction of the cephalosporin genes

Targeted gene disruption efficiency in Acremonium chrysogenum was increased 10-fold by applying the double-marker enrichment technique to this filamentous fungus. Disruption of the mecB gene by the double-marker technique was achieved in 5% of the transformants screened. Mutants T6 and T24, obtained by gene replacement, showed an inactive mecB gene by Southern blot analysis and no cystathionine-gamma-lyase activity. These mutants exhibited lower cephalosporin production than that of the control strain, A. chrysogenum C10, in MDFA medium supplemented with methionine. However, there was no difference in cephalosporin production between parental strain A. chrysogenum C10 and the mutants T6 and T24 in Shen's defined fermentation medium (MDFA) without methionine. These results indicate that the supply of cysteine through the transsulfuration pathway is required for high-level cephalosporin biosynthesis but not for low-level production of this antibiotic in methionine-unsupplemented medium. Therefore, cysteine for cephalosporin biosynthesis in A. chrysogenum derives from the autotrophic (SH(2)) and the reverse transsulfuration pathways. Levels of methionine induction of the cephalosporin biosynthesis gene pcbC were identical in the parental strain and the mecB mutants, indicating that the induction effect is not mediated by cystathionine-gamma-lyase.

Characterization of the reverse transsulfuration gene mecB of Acremonium chrysogenum, which encodes a functional cystathionine-gamma-lyase

In Acremonium chrysogenum, biosynthesis of cysteine for the formation of cephalosporin has been proposed to occur through the reverse transsulfuration pathway. A gene, named mecB, has been cloned from an A. chrysogenum C10 genomic library in lambdaEMBL3-ble. The cloned DNA fragment encodes a protein of 423 amino acids with a deduced molecular mass of 45 kDa that shows great similarity to cystathionine-gamma-lyases from Saccharomyces cerevisiae and other eukaryotic organisms. The protein was shown to be functional because it restores growth on methionine to A. nidulans C47 (mecB10), a mutant that is known to be defective in cystathionine-gamma-lyase. The cloned gene did not complement A. nidulans mecA or metG mutants. Enzyme activity assays confirmed that the cloned mecB gene encodes a cystathionine-gamma-lyase activity. The mecB gene is present in a single copy in the wild-type A. chrysogenum (Brotzu's strain) and also in the A. chrysogenum strain C10, a high cephalosporin producer. The gene is localized on chromosome VIII (5.3 Mb), as shown by hybridization to A. chrysogenum chromosomes resolved by pulsed-field gel electrophoresis. Transcription of the mecB gene gives rise to a major transcript of 1.5 kb and a minor one of 1.7 kb. The transcript levels were not significantly affected by addition of DL-methionine to the culture, indicating that expression of this gene is not regulated by methionine. The availability of this gene provides a very useful tool for understanding the proposed role of cystathionine-gamma-lyase in splitting cystathionine to supply cysteine for cephalosporin biosynthesis.

An integrated anaerobic--physico-chemical treatment concept for wool scouring wastewater

The strong flow wastewater from a wool scouring industry is treated by a combination of anaerobic digestion and physico-chemical postreatment. Based on previous laboratory results (Gutiérrez et al., 1999), three anaerobic baffled reactors (ABR) of 300 m3 each were built, processing 60% of the strong flow of a wool scouring mill for about two years. COD and grease removal in the anaerobic reactors were 47-50% and 50-55% respectively, with an organic load between 8.9 and 6.7 kg COD/m3 d. The effluent of the anaerobic reactors was assayed with additives in an industrial decanter centrifuge. As results of these assays, all the effluent of the three reactors was sent to the decanter centrifuge after dosing additives. Overall COD and grease removal of the integrated system were 87% and 93% respectively. Dosage of coagulation-flocculation additives was optimized in a continuous flocculation device. The proposed treatment is cheaper and easier to control than others alternatives with COD removal higher than 93%.

Overexpression and lack of degradation of thaumatin in an aspergillopepsin A-defective mutant of Aspergillus awamori containing an insertion in the pepA gene

A gene encoding the sweet-tasting protein thaumatin (tha) with optimized codon usage was expressed in Aspergillus awamori. Mutants of A. awamori with reduced proteolytic activity were isolated. One of these mutants, named lpr66, contained an insertion of about 200 bp in the pepA gene, resulting in an inactive aspergillopepsin A. In vitro thaumatin degradation tests confirmed that culture broths of mutant lpr66 showed only a small thaumatin-degrading activity. A. awamori lpr66 has been used as host strain for thaumatin expression cassettes containing the tha gene under the control of either the cahB (cephalosporin acetylhydrolase) promoter of Acremonium chrysogenum or the gdhA (glutamate dehydrogenase) promoter of Aspergillus awamori. Residual proteolytic activities were repressed by using a mixture of glucose and sucrose as carbon sources and L-asparagine as nitrogen source. Degradation of thaumatin by acidic proteases was prevented by maintaining the pH value at 6.2 in the fermentor. Expression of cassettes containing the gdhA promoter was optimal in ammonium sulfate as nitrogen source, whereas transformants expressing the tha gene from the cahB promoter yielded higher thaumatin levels using L-asparagine as nitrogen source. Under optimal fermentation conditions, yields of 105 mg thaumatin/l were obtained, thus making this fermentation a process of industrial interest.